This invention relates to an electroacoustic transducer and a method for its manufacture.
Various types of miniature electroacoustic transducers or microphones are known such as the electroacoustic microphone shown in FIGS. 1 and 2 of the drawings, which is provided with an electrically conductive cylindrical casing 10 having an opening 12 for receiving sound waves. Base 14 is disposed in casing 10 and includes a recess 16 on its upper side facing opening 12 and aperture 18 in its center. Stationary electrode 20 is secured in recess 16 of base 14, and includes a plastic film 22 on metal plate 24 which functions as a conventional electret film.
Electrically conductive diaphragm 26 is mounted in parallel with opening 12 and stationary electrode 20, with the periphery of diaphragm 26 clamped between insulation spacer 28 mounted on stationary electrode 20 and electrically conductive ring 30 secured to the inner wall of casing 10. Diaphragm 26 is made, for example, of a metal film or a plastic film coated with a metal film and having a thickness of several microns. Metal plate 24 of stationary electrode 20 has protruding pin 32 on its under side to penetrate through hole 18. Protruding pin 32 and casing 10 function as as signal output terminals which is coupled to the desired circuit (not shown).
The electroacoustic microphone shown in FIGS. 1 and 2 is a rather complicated structure and presents problems from the standpoint of its operational characteristics, cost, size, and manufacturing process.